The present invention relates to a radio transceiver and, more particularly, to a radio transceiver for use in a mobile radio communications system.
In a mobile radio communications system, such as a cellular telephone system, the number of frequencies assigned to a base station has been increasing to ease a strong demand. In addition, a single frequency is reused in a certain small area for effective use of the frequencies. Thus, a receiver used in, for example, a mobile station may receive more than one frequency.
The received signal is first applied to a radio frequency (RF) amplifier followed by a frequency converter, or mixer. The RF amplifier is set to have a high gain in order to increase the reception sensitivity. As a result, the mixer produces undesired sums and differences of the received two or more frequencies due to its non-linearity and overloading. The undesired sum and difference frequencies are commonly referred to as intermodulation distortion which deteriorates the speech quality of telephone communication.